In many fiber optic cable assemblies, it may be necessary to remove the outer jacket layers of the cable and expose a length of fiber that is then inserted into a smaller diameter furcation tube. This may be done because a robust fiber optic cable normally has a jacket diameter that is too large to fit into standard fiber optic connectors, whereas a smaller diameter furcation tube can fit into such connectors. Unfortunately, this transition technique leaves a gap between the furcation tube and the cable jacket, which exposes a section of the fiber to the environment. It also breaks the continuity of strength members in the cable that are designed to absorb the tensile load of the assembly rather than subjecting the fiber to the load. Similar exposure of fibers may occur when a fiber optic cable is broken out (i.e., “furcated”) into multiple branches of fibers or subgroups of fibers, each with its own furcation tube.
One solution for covering the gap between the jacket and the single furcation tube utilizes a close fitting plastic tube (transition tube) that fits over the gap. Once it is in place, the transition tube is filled with epoxy. The epoxy mechanically binds the strength members from the furcation tube and the cable together to avoid having the fiber carry any tensile load. In addition, the epoxy fills the gap, thereby preventing contamination or environmental attack of the fiber. The transition tube and the sections of the furcation tube and cable immediately adjacent the furcation tube are covered with a piece of adhesive lined heat shrink tubing. During a heating process to shrink the heat-shrink tubing, the adhesive lining the tubing melts and forms a bond between the transition tube and the inner surface of the heat-shrink tubing. The heat shrink tubing adds UV and abrasion resistance to the assembly.
Although this technique is commonly employed, it has some disadvantages. The epoxy is expensive due to its initial cost, pot life, unrecoverable waste, and the slow rate of cure. Also, it involves a number of different components and a good deal of labor to complete. Thus, a technique that reduces or eliminates these shortcomings may be desirable.